On gas turbines, especially with annular combustors, it can occur that undesirable emissions like carbon monoxide are temporarily increased above acceptable levels (usually for several minutes or hours) due to flame out of one burner of the plurality of burners present in the combustor. Such a flame out can be maintained during stable load operation for several hours. This temporary increase in emissions—especially carbon monoxide emissions—can lead to an infringement of a contractual agreement on emission guarantees.
This problem up to now has been solved by changing orifice diameters in the coupling delivering gas fuel to the respective burners. The diameter of the orifice which is associated with the burner flaming out is usually changed to an orifice with larger diameter in order to deliver more gas fuel to this burner. This solution requires the gas turbine to be stopped at least for 30 minutes. Most often such a stop is not acceptable. Further the increased orifice diameter on one burner moves the flame out problem to another burner on a later date and is therefore not solving the issue completely.
Another conventional solution is to install manual valves in the fuel supply line upstream of each burner coupling and change their opening position while the gas turbine is in operation. This solution does not require the gas turbine to be shut down to solve the problem but it requires having expert personal at site to operate the manual gas valves.